Concern with population growth has led to greater awareness of both individual and societal needs for fertility regulation. In an increasing number of countries modern contraceptives and safe abortion are now available. There is much agreement that effective fertility regulation requires at least two kinds of decisions: (a) to delay or prevent childbirth at a given time, and (b) to choose a method for achieving that goal. Because family planning is inevitably related to a sexual relationship, couple interaction is of paramount importance in identifying its determinants. Israel offers a natural laboratory to examine the interaction of couples who are situated at various points on a continuum of modernity, and to whom modern contraception and safe abortion (although nominally illegal), have been available for several years. For the purposes of the proposed study, 1,800 Jewish and Arabic couples, divided into subgroups of varying modernity, consisting of Jews of European/ American, Israeli, & Afro-Asian origins, and urban and rural Arab couples from both Israel and the Occupied Territories, will be interviewed with regard to their subjective assessment of fertility-regulating means, their interaction and exchange of information with their marital partners, and the decision-making processes leading to their choice and use of fertility-regulating methods. An objective assessment of the degree of consensus and accuracy of mutual perception between them will also be made. Implications will be examined not only for Israeli society but also for other countries, including the United States of America.